This invention relates to a method of group-supervising an elevator system where a plurality of cages are controlled so as to stand by.
In a case where a plurality of cages are juxtaposed, a group supervision operation is usually performed. One system of the group supervision operation is an assignment system. In this system, as soon as a hall call is registered, assignment estimation values are calculated for the respective cages, whereupon the cage of the best estimation value is selected and assigned as a cage to-serve, and only the assigned cage is caused to respond to the hall call, thereby intending to enhance the service efficiency of the elevator system and to shorten the wait times of hall calls. Besides, in order to make the assignment system efficient, cages (hereinbelow, termed "unoccupied cages") which have responded to cage calls and allotted hall calls and have completed their services are caused to dispersively stand by at proper floors. There are the following schemes for the dispersive standby:
(a) The service floors of a building or an elevator system are divided into a plurality of blocks, in each of which one cage or two cages is/are caused to stand by in accordance with predetermined priority levels. (Official gazettes of Japanese Patent Applications Laid-open No. 73755/1978, No. 56958/1980 and No. 111373/1980, and so on)
(b) The arrival expectation times of cages for arriving at a specified floor are compared with a predetermined period of time set in correspondence with the specified floor, thereby to decide if an unoccupied cage which can arrive within the predetermined time and which is standing by is existent. In the absence of the unoccupied cage which is standing by, the unoccupied cage is moved to, and caused to stand by in, either of the specified floor and a floor from which the cage can arrive at the specified floor within the predetermined time. (Official gazette of Japanese Patent Application Publication No. 37187/1986)
(c) An unoccupied cage is moved to stand by in a floor which is nearest to the middle point of the longest one of the cage intervals between other cages except for the unoccupied cage. (Official gazette of Japanese Patent Application Publication No. 17829/1982)
(d) Unoccupied cages are moved to stand by so that the intervals between the unoccupied cages or between floors in which the cages stop may become a predetermined value or less. (Official gazette of Japanese Patent Application Laid-open No. 48366/1984)
(e) Traffic volumes in a building (the numbers of persons getting on and off) are collected for individual floors, floors in which cages stand by and numbers in which the cages stand by are determined according to the traffic demands, and the cages are caused to dispersively stand by on the basis of-the standby floors as well as the standby cage numbers. (Official gazette of Japanese Patent Application Laid-open No. 138580/1984)
(f) The numbers of hall calls registered are collected, and floors where more hall calls occur are determined as standby floors, in which cages are caused to dispersively stand by. (Official gazette of Japanese Patent Application Laid-open No. 62176/1982)
The above schemes, however, involve problems as stated below:
With the scheme (a), unless the dispersive standby floor has one standby cage (two cages in each of some floors) corresponding thereto, a cage standing by in another floor is drawn to the standby floor. Accordingly, this cage is specially run to the standby floor even when a cage exists near the pertinent standby floor. Such an operation becomes a wasteful run, and incurs a useless power consumption. Therefore, the scheme (b) has been proposed, and when the cage exists near enough to arrive at the standby floor within the predetermined time, it need not be specially run to the standby floor. In a case where all the cages of the elevator system are unoccupied cages, it is satisfactory that, as in the scheme (a) or (b), the cages of the plurality of blocks (zones) are individually caused to dispersively stand by in accordance with the predetermined priority levels. However, in a case where any cage is operating in response to the cage call or the allotted hall call, it is difficult to say that the dispersive standby conforming to the priority levels is always appropriate. It becomes important to predict the movement of the operating cage in the near future and to select on the basis of the prediction the standby floors in which the unoccupied cages are to stand by.
This point will be explained with reference to FIG. 13. It is assumed that a building in which three cages are installed is divided into three zones Z.sub.1, Z.sub.2 and Z.sub.3 as illustrated in FIG. 13, and that unoccupied cages are caused to dispersively stand by in accordance with the priority levels of Z.sub.1 .fwdarw.Z.sub.3 .fwdarw.Z.sub.2. It is also assumed that the cages A and B are unoccupied, whereas the cage C is operating in order to respond to the down call 6.sub.d of the sixth floor and the cage call 1.sub.c of the first floor. When the scheme (a) is applied on this occasion, the cages A and B are respectively caused to dispersively stand by in the zones Z.sub.1 and Z.sub.3 in spite of the situation that the cage C operating toward the zone Z.sub.1 can respond in the shortest time to a hall call which will occur near the first floor in the near future. Accordingly, the cages A and C will stand by in the first floor together after 20 odd seconds, and the dispersive standby operation is not effective for shortening the wait time of the hall call. Eventually, the cage A or C is run to stand by in the zone Z.sub.2, and useless power is consumed again as stated before. The same problem is left unsolved in the scheme (b).
In addition, there are schemes wherein, as in the schemes (c) and (d), the standby floors are determined so as to establish uniform cage intervals. However, while any cage is operating in order to respond to a call, the cage intervals change every moment, and hence, the standby floors must be changed in conformity with the changing intervals. Thus, the problem of increased wasteful runs is not solved. Further, there are schemes wherein, as in the schemes (e) and (f), the floors in which hall calls are liable to occur, or floors which are near the former floors are determined as the standby floors. It is wasteful, however, that the unoccupied cage is caused to stand by in spite of the presence of the cage operating toward the pertinent floor as explained with reference to FIG. 13. Moreover, although the hall call is liable to occur, the occurrence is random. Therefore, in a case where a hall call occurs earlier at another floor, the wait time of this hall call may possibly become long.
In this manner, in the case where one or more cages are operating in order to respond to the calls in the mode of the dispersive standby of the unoccupied cages, the prior-art schemes have the problems of the prolonged wait times and increased wasteful runs.
There has also been proposed a scheme (g) as stated below wherein, when a hall call has occurred anew with all cages standing by as unoccupied cages, floors in which the respective cages will become unoccupied in the future when assigned to the hall call are predicted, and that an appropriate one of the cages which will establish the state of the dispersive arrangement of the cages also after the end of its service to the hall call is selected and is assigned to the hall call. This assignment scheme is intended to dispense with the dispersive standby operation after the end of the service and to prevent the wasteful operations of the unoccupied cages.
(g) A group-supervisory elevator system wherein cages are caused to stand by at alighting positions when a hall call has occurred anew, the hall call is tentatively allotted to each of the cages in succession so as to predict the alighting position of the tentatively assigned cage, the degree of dispersion of the cages is calculated from the predicted alighting position of the tentatively assigned cage and the positions of the other cages, such degrees of dispersion are used as estimation values of the respective assigned cages so that the cage affording a higher degree of dispersion may be assigned more easily, and the cage to be assigned to the hall call is determined from the estimation values of the respective cages. (Official gazette of Japanese Patent Application Publication No. 56076/1987)
However, the assignment scheme as stated above, which is intended to control the cages at the occurrence of the hall call so that the cage arrangement in the future (the cage arrangement at the point of time at which the tentatively assigned cage is alighted from) may become appropriate, is applicable only in the limited situation where the hall call has occurred and where all the cages are unoccupied cages. In particular, when an unexpected hall call occurs anew before obtaining the result of the last hall call allotment (that is, before the realization of the cage arrangement as expected), the last hall call allotment prolongs the wait time of the new hall call. Accordingly, it is readily conjectured that the wait time of a hall call within a predetermined period of time will consequently lengthen. As thus far described, it is unreasonable to substitute the hall call allotment for the function of the dispersive standby operation, and it is necessary for shortening the wait time to disperse the unoccupied cages for standby before the occurrence of the hall call.